The 3GPP (3rd Generation Partnership Project) standards organization has now proposed a new-generation evolved network architecture, in which a core network part is an SAE (SystemArchitecture Evolution) network and an access network part is an LTE (Long Term Evolution) network, also called an E-UTRAN (Evolved Universal Terrestrial Radio Access Network). The E-UTRAN is formed by eNBs (evolved NodeBs). The SAE network is formed by two parts: MME (Mobility Management Entity) and SAE gateway. SAE gateways include a serving gateway (Serving Gateway) and a PDN Gateway (Packet Data Network Gateway). An MME is a node on a control plane of the core network part and is in charge of managing a context of a UE (User Equipment) and bearers on a user plane. A serving gateway takes care of transmitting subscriber service data, and a PDN Gateway is in charge of transmitting subscriber signaling data.
When a UE is performing a VOIP (Voice over Internet Protocol) service in a PS (Packet Switched) domain of an SAE/LTE network, if a CS MT-LR (Mobile Terminated Location Request) procedure is triggered due to a location service of a CS (Circuit Switched) domain, an SRVCC (Single Radio Voice Call Continuity) procedure needs to be executed to hand over the UE back to the CS domain. After the UE is handed over back to the CS domain, an MSC for previous combined attach notifies the UE of providing location information. In this scenario, if the selected MSC does not have an SRVCC capability, the UE is unable to complete the location service of the CS domain.